Anterior segment ocular coherence tomography

A practical tool for the comprehensive ophthalmologist

Abstract

Ocular coherence tomography (OCT) provides non-invasive and rapid in vivo imaging of ocular structures using low coherence interferometry. It first appeared in 1991 for imaging of the posterior segment of the eye; shortly thereafter, the utility of OCT was expanded to the anterior segment (AS-OCT). With improvements in technology including higher resolution and rapid capture speed of images, AS-OCT has become an integral tool for current-day cornea specialists in the clinical evaluation of the cornea and anterior segment. AS-OCT pachymetry is often used to analyze corneal thickness while cross-sectional images assist with the visualization and morphometric analysis of the anterior segment. These features are commonly used to assess endothelial graft attachment and corneal graft health. Though AS-OCT has been used predominately by cornea specialists, it does have wide-spread application for the comprehensive ophthalmology practice. Moreover, the advent of affordable imaging attachment lenses has also made AS-OCT a more practical tool to have in the clinic.

A comprehensive ophthalmologist can use AS-OCT to monitor pathologies such as recurrent corneal erosions, Salzmann Nodular Degeneration, depth of scarring and endotheliitis. It can also be used in the pre- and post-operative assessment for cataract surgery. For example, AS-OCT can be used to help assess the likelihood of whether a patient with Fuchs’ dystrophy may develop corneal decompensation following cataract surgery. This information can in turn help navigate shared clinical decision making by informing the patient about the risks and benefits of surgery pre-operatively. In the post-operative setting, mild corneal edema is common and expected. However, if there is edema which is out of proportion to either the surgeon’s expectations or the amount of energy from the surgery, a closer look to find the etiology of the edema is warranted. AS-OCT can be used to help delineate common causes of corneal decompensation following cataract surgery including Descemet’s membrane (DM) detachment, retained lens fragments, or infectious causes. We present four clinical scenarios, one of which is the use of AS-OCT in pre-operative assessment and three cases in which AS-OCT is used to identify post-operative complications.